A game that involves cutting a face-hole in a 55 gal trash bag and crouching down inside the bag (to look like trash) in a driveway or on a porch. The object of the game is to frighten residents, trick-or-treaters, or unsuspecting pizza delivery guys.

The Urban Dictionary T-Shirt

The act when a man inserts his own testicles into his own anus or someone elses. The etymology being taken from the concept of tea-bagging however in this circumstance the reference to trash connotes the dirtiness of shit.

Did you see the video where the guy trash-bagged himself?
Do you enjoy trash-bagging